Introduction

Mastigoteuthids are deep water pelagic or benthopelagic squids that are morphologically distinctive. They are weakly muscled, reddish in color and have elongate fourth arms and whip-like tentacular clubs. Much of the red pigment is not in chromatophore organs but dispersed in other integumental cells, although chromatophores are present. The Mastigoteuthidae, however, is among the most taxonomically confused families of all deep-sea squid due to the fact that many characters are based on the structures (tentacles and skin photophores) often lost during capture.

The whip-like tentacles have tentacular clubs that are little differentiated from the tentacular stalks eventhough they are covered with thousands of minute suckers. In some species, the suckers are so small as to be invisible to the naked eye. The photograph below shows the midregion of a tentacular club with the sucker-bearing portion marked by an X. The arrow points to a microscope enlargment showing the small suckers. Such small suckers, at least in freshly dead specimens, seem to function much like "fly paper" in that anything touching them, whether large or small, sticks.

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Figure. Side view of a portion of the tentacle club (bottom) of Magnoteuthis microlucens, Hawaiian waters, showing the club covering the top half of the cyclindrical tentacle. Insert - Portion of the club, marked by an "X", as seen through a microscope. Photographs by R. Young.

Fins are usually very large and positioned mostly posterior to the muscular part of the mantle. No well-developed system of giant nerve fibers is present, which reflects the absence of rapid jet propulsion (Dilly, et al., 1977).

*Funnel pocket (arrow) extends between funnel bridles deep into the head to the cephalic vein. Presence of the pocket can be recognized in the paralarval stage onward (at least in M. famelica).

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*Funnel locking-apparatuses have three major forms.

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*Integumental photophores are of three types. Those of Mastigoteuthis (below left) and M. pyrodes (below middle) look superficially the same. Those of Magnoteuthis microlucens (below right) are much smaller and very difficult to see (in the photograph they are apparent since most of the covering chromatophore-bearing skin has been lost during capture.

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*Eyelid photophores (arrows) occur in three sizes. Compare Small and Medium sizes with the size of the nearby integumental photophores. Species with Large eyelid photophores lack integumental photophores.

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**Chromatophores. See photographs of integumental photophores above. Count the number of chromatophores between photophores in Mastigoteuthis and in M. pyrodes to see the difference between "scattered" and "abundant" chromatophores. See the Mastigoteuthis page to compare the integument of these two genera.

Discussion of Phylogenetic Relationships

The genera in the family are all distinct. The relationships between genera are not clear. M. pyrodes may be closest to Mastigoteuthis and Echinoteuthis as they all share a funnel pocket (this feature, however, is probably a pleisiomorphy) and an eyelid photophore. The presence of integumental photophores over much of the ventral surfaces may indicate closer relationship to Mastigoteuthis, but the structure of the photophores has not been examined in M. pyrodes, and they superficially appear to be different from those of Mastigoteuthis spp. Species in all the above genera share long, slender clubs with sucker orifices dominated by pegs on the outer ring and not teeth on the inner ring. Idioteuthis cordiformis and Mastigopsis hjorti show many similarities (absence of funnel pocket and skin photophores, relatively short tentacular clubs with large suckers whose orifices are dominated by teeth on the inner rings, large fins, virtually identical skin tubercules and probably have a common ancestor. Species Magnoteuthis have uncertain relationships based on morphology. They are similar to M. cordiformis and M. hjorti in the absence of a funnel pocket but have tentacles more similar to the other species in the other genera.

Two studies have used molecular data to determine relationships in the family. The first study was based on three genes from ten individuals in four species and used a related species, Joubiniteuthis portieri, as the outgroup. This study yielded the single tree (L= 515, CI= 89, RI= 90) (Young et al., 2008) seen below. These limited data suggested that M. hjorti may be the closest relative of the M. magna-group.

A more recent study (Braid, et al., 2013) was based on the same three genes and most of the DNA data from the first study. In all, however, they had data from 28 squid, including three outgroup species (Chiroteuthidae: Chiroteuthis cf. mega, Asperoteuthis nesisi; Joubiniteuthidae: Joubiniteuthisprotieri) and eight species of mastigoteuthids in forming the following tree:

A Bayesian maximum clade credibility tree indicated relationship between E. atlantica and Mastigoteuthis species with posterior probability of 100 and relationship between Mastigopsis hjorti and Magnoteuthis spp. with posterior probability of 76. I. cordiformis did not group with either of these clades but came off the tree in a basal position. The authors question the position of I. cordiformis within the family. Lindgren (2010) in broader phylogenetic studies of the Oegopsida and Lindgren et al., (2012) of the Cephalopoda (2012) found that the mastigoteuthids examined did not form a natural group. While the genera presently recognized within the family are very distinct, the family may not be.

Nomenclature

In previous versions of this page, all species were placed in a single genus Mastigoteuthis and within this genus they were placed into species groups. Recently, the family has been reviewed based on both morphology and a strong input from molecular analysis (Heather et al., (2013). They reviewed earlier classifications and verified the species groups previously used here but their DNA analysis was sufficiently robust (see section on "Discussion of Phylogenetic Relationships" above) to warrant placing these groups in genera, which they did. Their terminology has been adopted here.

Behavior

Two species (Mastigopsis hjorti, Magnoteuthis magna) have been observed from submersibles drifting just above the ocean floor with tentacles dangling within a few mm of the bottom, presumably, to capture copepods and other small plankters of the epibenthic zooplankton (Roper and Vecchione, 1997). The tentacles extend from the tips of the ventral arms (arms IV) from where they reside in the tentacular sheaths (i. e., between the arms and their lateral membranes). The tentacles are typically held apart by the ventral arms (the "tuning fork" posture) so they "fish" independently of each other (Roper and Vecchione, 1997).

About This Page

Page: Tree of Life
MastigoteuthidaeVerrill, 1881.
Authored by
Michael Vecchione, Richard E. Young, and Annie Lindgren.
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